Motion sensitive explosive with a delay mechanism

ABSTRACT

A motion sensitive explosive device is kept in a safe unarmed condition by a pair of silicone gum plugs which have been expanded by absorption of a fluoro-carbon fluid such as FREON. The expanded plugs hold a trip lever arm immovable against a detent when the device is being deployed. The device when implaced is armed, after a time delay, by evaporation of the fluoro-carbon which causes shrinking of the plugs to their normal size and release of the lever arm. Upon subsequent slight movement of the device the trip lever releases a spring loaded firing pin so that it can strike and ignite an impact detonator.

[451 Jan. 22, 1974 United 0 States Patent [191 Zacharin [54] MOTION SENSITIVE EXPLOSIVE WITH A 3,738,276 6/1973 Picard et 102/7.2

DELAY MECHANISM Inventor:

Alexey T. Zacharin, Parsippany, Primary Examineh'samud Engle NJ.

Attorney, Agent, or Firm--Edward J. Kelly; Herbert Berl; A. Victor Erkkila [73] Assignee: The United States of America as [57] ABSTRACT A motion sensitive explosive device is kept in a safe represented by the Secretary of the Army, Washington, DC.

Jan. 3, 1973 [22] Filed? unarmed condition by a pair of silicone gum plugs which have been expanded by absorption of a fluoro- [2i] Appl. No.2 320,797

carbon fluid such as FREON. The expanded plugs hold a trip lever arm immovable against a detent when the device is being deployed. The device when im- [52] U.S. 102/8, 102/70 R [51] Int. F42b 23/26 Field of Search placed is armed, after a time delay, by evaporation of 58 1 102/8 7 70 83 the fluoro-carbon which causes shrinking of the plugs to their normal size and release of the lever arm. Upon subsequent slight movement of the device the trip [56] References Cited UNITED STATES PATENTS lever releases a spring loaded firing pin so that it can Mettler...................................

I r. We 0 I] m F n g 0 n t we d m a a m c n 4 .m d

3,094,935 6/1963 3,138,100 6/1964 Peschko......................... 3,254,602 6/1966 Klostermann et al.........

MOTION SENSITIVE EXPLOSIVE WITH A DELAY MECHANISM GOVERNMENTAL INTEREST The invention described herein may be manufactured, used and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION Various means have been used in the prior art to make a sensitive mechanical disturbance device. Some of the prior art devices incorporate a trip lever and a free ball to act as the tripping mass for a lever release spring loaded firing pin. These prior art mechanisms in order to work properly must be tilted to allow the activating ball to travel a given distance in order to gather enough energy to trip the lever. The problem with these prior art devices has been that they have failed to function when the device was carefully disposed of, that is moved without appreciably changing its initial position. In cases where the prior art device was made more sensitive to slight changes in motion, the danger often arose of an inadvertent malfunction and subsequent injury to the emplacing personnel. Some prior art devices utilizing delay mechanisms in conjunction with motion sensitive triggering means have utilized the dashpot, piston and cylinder arrangements as a delay means. The problem encountered with these prior art devices hasvbeen the increased cost in making piston and cylinder fits to exact dimensions so that the time delay could beheld relatively constant. Another problem with use of the prior art dashpot delay mechanisms in explosive devices has been the fluctuation of its time delay as a function of environmental temperature. This fluctuation occurs because .of the change in viscosity of the dampening fluid and difference in expansion coefficicuts of different parts with the resultant slowing down of the piston through the fluid medium.

SUMMARY OF THE INVENTION The present invention relates to a motion sensitive explosive device which has a time delay means therein for holding the explosive device in a safe unarmed state while the explosive device which is attached thereto is being implaced in a target area such as a mine field. Two oppositely disposed silicone gum rubber plugs; when saturated with a fluorocarbon expand toward each other and fixedly hold therebetween a detent and triplever which prevents a spring loaded firing pin from being actuated. After dispersal and a period of time has elapsed which allows the fluorocarbon fluid toevaporate through a porous plug, the silicone rubber plugsjgshrink in size freeing the trip lever so that it will unlatch the spring loaded firing pin and activate a detonator, upon the slightest movement.

One of the objects of the present invention is to provide a motion sensitive explosive device with a time delaymherein, the time delay means being responsive to the evaporation of a fluorocarbon fluid.

Another object of the present invention is to provide a motion sensitive explosive device with a time delay therein, the time delay means holds a trip lever adjacent to. a fixed detent so that the lever cannot move when the device is being implaced and thereby holds thedevice in a safe condition.

Another object of the present invention is to reduce the safety hazard in handling a motion sensitive exlosive device during dispersal and to increase the sensitivity of the device when the device has been implaced and put into an armed condition.

Another object of the present invention is to provide a motion sensitive device with a time delay wherein after ground implacement any relative motion between a housing and a body which is cantilever spring mounted therein causes the latter to vibrate upon disturbance of the device thereby causing a lever arm to release a spring loaded firing pin so that it will forcibly strike a detonator.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric partial cut-away view of the motion sensitive device shown as it would appear in its normal mounting position located in a booby trap or mine.

FIG. 2 is an isometric partial cut-away view taken along line 2-2 of the lower section of FIG. 1.

FIG. 3 is a partial cross-sectional view taken along line 3--3 of FIG. 2 of the time delay in the housing showing how the detent pin and the lever arm are held by the expanded rubber silicone plugs when the device is in a safe position.

FIG. 4 is a partial cross-sectional view taken along line 2-2 of FIG. 1 showing the motion sensitive device in an armed position with the rubber plugs in a contracted state, with the detent pin and the lever arm adjacent and in-line contact with each other.

FIG. 5 is a partial cross-sectional view taken along line 5-5 of FIG. 4 showing the relative positions of the rubber plugs, detent pin, lever arm and housing slot when the motion sensitive device is in an armed position.

FIG. 6 is a partial cross-sectional view taken along line 2-2 of FIG. 1 showing the motion sensitive device in its fired" position, with the lever arm tripped and the firing pin impacting on the detonator.

FIG. 7 is a partial ross-sectional view taken along line 77 of FIG. 6 showing the position of the lever arm detent, and rubber plugs in their retracted condition.

Throughout the following description like reference numerals are used to denote like parts of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. I a housing 10 completely en closes and protects the body 12 of the motion sensitive device 14. The sensitivity of the device is derived thru the concentration of body mass 12 held in cantilever fashion by L-shaped spring leaf 16 which has one end 18 fixedly attached to housing 10 and its other free end 20 fixedly attached to the body 12. Spring leaf 16 holds the body in static equilibrium. By controlling the spring leaf stiffness the desired level of sensitivity to motion can be selected. A pair of oppositely disposed silicone rubber plugs 22 and 22', only one of which is shown in FIG. 1, are operatively positioned in the housing I0 and the body 12 and retained therein by a pair of porous end caps 24 and 24'.

Referring now to FIG. 2, a detent pin 26 is fixedly positioned in the housing and acts as a stop for the rounded end 28 of lever arm 30. Lever arm 30 is rotatably positioned in body slot 32 by pivot 34. The other end 35 of lever arm 30 retains a cocked firing pin 36 which is biasedly positioned in firing pin bore 38 by coil spring 40. The coil spring 40 is held in compression by the firing pin 36 on one end and on its other end by a retainer 42 which is threadedly attached to the body 12. A detonator 44 is axially positioned in the body 12 so that it is aligned with the firing pin 36.

FIG. 3 shows a cross-sectional view of how the rubber plugs 22 and 22' are retained by the porous end caps 24 and 24' and in housing delay bores 46 and 46', and how the FREON expanded rubber plugs 22 and 22 also slidably pass through the body delay bores 48 and 48 to hold the rounded end 28 of the lever arm 30 immediately adjacent to the detent pin 26 so that the former can not inadvertently slip over the latter through body slot 32.

FIG. 4 shows the motion sensitive device in an armed condition having rubber plugs 22 and 22' retracted so that the rounded end of lever arm 30 is no longer restrained from moving away from the detent pin 26 with which it has only line contact. Under the armed condition the body 12 and the lever arm 30, to which it is rotatably attached by pivot 34, become sensitive through the concentration of mass of the body 12 suspended from the free other spring end of spring leaf 16 as shown in FIG. 1.

FIG. 5 shows in cross section view how the rubber plugs 22 and 22 have shrunk in size due to the evaporation of the fluorocarbon fluid thru the porous end caps 24 and 24', thereby freeing the end 28 of the lever arm 30 so that it can slip off of the detent pin 26 and pass over it through body slot 32 when the device is moved.

FIG. 6 shows the motion sensitive device in the fired" condition. In the fired condition the lever arm 30, because of some vibrations given to the body 12, has slipped past the detent pin 26 and moved in a counter-clockwise direction in slot 32. The rotation of the lever arm 30 has moved the other end 35 of the lever arm 30 away from the firing pin 36 thereby allowing the latter to forcibly impact upon a detonator 44 which is held in body 12 in a detonator bore 50 and inline with said firing pin 36.

FIG. 7 shows in a cross-sectional view how the rubber plugs 22 and 22 have freed the lever arm 30 so that it can slip over detent pin 26.

In operation, the device is stored in a container (not shown in the drawings) which has been filled with FREON or other fluorocarbon which permeates thru the porous end caps 24 and 24'.

The fluorocarbon causes the silicone rubber plugs 22 and 22 to swell which aligns and immobilizes the rounded end 28 of lever arm 30 with the detent pin 26. The lever arm in the safe position detents the cocked firing pin 36. Upon tactical emplacement, the device is released from the aforementioned container and dropped on the ground. The FREON trapped inside of the housing 10 and the body 12 evaporates into the atmosphere through the porous caps 24 and 24' causing the rubber plugs 22 and 22' to shrink. Since evaporation of the FREON and shrinkage of the rubber plugs 22 and 22' requires a finite length of time, the device has time to come to a complete state of rest by the time the rubber plugs 22 and 22' release the rounded end 28 of lever arm 30 and the detent pin 26. The detent pin 26 and the lever arm 30 remain aligned with each other because the leaf spring 16 is made strong enough to support the body 12 without sagging. The device is in the armed condition once the rubber plugs 22 and 22 have shrunk. Since the coil spring 40 acting through the firing pin 36 produces a compressive force on the line contact surface between the detent pin 26 and the rounded end 28, any misalignment between the two contacting surfaces will cause one to slip over the other thereby allowing the lever arm 30 to rotate in a clockwise direction. This misalignment is induced when the device is stepped upon, kicked, lifted or in any way substantially moved from its rest position. The disturbance of the housing 10 is transmitted through the leaf spring 16 to the body 12 which initially because of inertia tends to remain stationary. The relative movement of the body 12 with respect to the housing 10 misaligns the detent pin 26 with the rounded end 28. The misaligned rounded end 28, because of the force being exerted on it by the coil spring 40 through the lever arm 30, jumps past the detent pin 26 and releases the firing pin 36, which forcibly impacts on the detonator 44 thus completing the devices intended mission.

The foregoing disclosure and drawings are merely illustrative of the principles of this invention and are not to be interpreted in a limiting sense. I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described for obvious modifications will occur to a person skilled in the art.

Having thus fully described the invention, what is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A motion sensitive explosive device'which comprises:

a housing having a pair of housing delay bores oppositely disposed therein;

a body flexibly mounted in said housing having a pair of delay body bores therein axially aligned with said housing delay bores, and a body slot having one end communicating with said housing;

a cantilever leaf spring having its fixed end attached to said housing, and its free end fixedly attached to said body;

a detent pin fixedly positioned in said housing having one end protruding into said body slot;

triggering means biasedly disposed within said body;

a detonator fixedly held in said body and axially aligned with said triggering means;

lever means rotatably positioned in said body slot for holding said triggering means in a locked safe position, insensitive to motion, when said explosive device is being ground implaced, and in an armed position sensitive to motion, when said device is at rest after being implaced;

delay means operatively held and slidably disposed in said housing and body bores for holding said lever means stationary in said safe position and for subsequently releasing said lever means in said armed position so that said triggering means impacts and fires said detonator when said device is subject to movement.

2. A motion sensitive explosive device as recited in claim 1 wherein said triggering means comprises:

said body having a firing pin bore therein;

a firing pin slidably positioned in said firing pin bore, said firing pin being stopped by said lever means when said device is in a safe" and armed condition;

a retainernthreadedly held in said body for closing one end of said firing pin bore; and

a coil spring biasedly held in compression imtermediate said firing pin and said retainer.

3.A motion sensitive explosive device as recited in claim 2 wherein said lever means comprises:

a lever arm rotatably positioned within said body slot having a rounded end making line contact with said detent pin when said device is in said safe and armed' conditions, and its other end in contact with said firing pin; and

a pivot fixedly held in said body for permitting said lever arm to rotate within said body slot.

4. A motion sensitive explosive device as recited in claim 3 wherein said delay means comprises:

a pair of silicone rubber plugs slidably held in said housing and body delay bores, for holding said detent pin and said rounded end of said lever arm intermediate therebetween;

a pair of porous end caps operatively positioned in said housing for retaining said rubber plugs in said delay housing bores; and

a fluorocarbon fluid operatively disposed in said housing and body for expanding said plugs when said device is in a safe condition and for evaporating from said housing and body so that'said silicone rubber plugs can contract releasing said lever arm when said device is in said armed condition. 

2. A motion sensitive explosive device as recited in claim 1 wherein said triggering means comprises: said body having a firing pin bore therein; a firing pin slidably positioned in said firing pin bore, said firing pin being stopped by said lever means when said device is in a ''''safe'''' and ''''armed'''' condition; a retainer threadedly held in said body for closing one end of said firing pin bore; and a coil spring biasedly held in compression imtermediate said firing pin and said retainer.
 3. A motion sensitive explosive device as recited in claim 2 wherein said lever means comprises: a lever arm rotatably positioned within said body slot having a rounded end making line contact with said detent pin when said device is in said ''''safe'''' and ''''armed'''' conditions, and its other end in contact with said firing pin; and a pivot fixedly held in said body for permitting said lever arm to rotate within said body slot.
 4. A motion sensitive explosive device as recited in claim 3 wherein said delay means comprises: a pair of silicone rubber plugs slidably held in said housing and body delay bores, for holding said detent pin and said rounded end of said lever arm intermediate therebetween; a pair of porous end caps operatively positioned in said housing for retaining said rubber plugs in said delay housing bores; and a fluorocarbon fluid operatively disposed in said housing and body for expanding said plugs when said device is in a ''''safe'''' condition and for evaporating from said housing and body so that said silicone rubber plugs can contract releasing said levEr arm when said device is in said ''''armed'''' condition. 